With the continued and ever-increasing demand for portable communication devices coupled with the advance of various technologies, it has been desirable to provide the ability of portable communication devices to communication in different frequency bands. The ability to use multiple frequency bands has many advantages, for example, permitting communications in different locations around the world in which one or more of the different bands are used, providing a backup so that the same information can be provided through the different bands, or permitting different information to be provided to the device using the different frequencies and permitting the device to determine the manner in which to respond to the different information.
Although a system of separate antennas may be employed in which the individual antennas are electronically and/or mechanically switched in and out of operation as desired, such a system has multiple problems: it is expensive, requires complex algorithms to effectuate the switching, consumes a substantial amount of power to switch from one antenna to another, can generally only handle low power transmissions, and introduces a significant amount of distortion causing out of band energy spreading over many spurious frequencies. It is thus desirable to limit the number of separate antennas to a single combined passive structure that functions in the multiple bands. One particularly useful combination of bands includes ultra high frequency (UHF) band (about 380-540 MHz and 770-870 MHz) and the Global Positioning Satellite (GPS) band (about 1.575 GHz). This combination is particularly desirable for public safety providers (e.g., police, fire department, emergency medical responders, and military) who have traditionally used the UHF band maintained exclusively for public safety purposes. With the advent of GPS, it has become desirable to be able to determine locations of the public safety providers to better manage increasingly scarce resources, coordinate quicker response, and guide personnel safely through potentially dangerous situations.
It is especially challenging however to combine individual antennas with these bandwidths into a single structure. Although it is desirable to provide an antenna structure with minimized physical dimensions while maximizing signal response, designing antenna structures with these features becomes increasingly more difficult as the number of bands to be covered increases. For example, current high-performance dual-band antenna structures have an increased length or have a substantially larger diameter so that the antenna structure is not mechanically flexible enough to meet mechanical (drop or bend) tests designed to ensure the reliability of the radio. Additionally, the length and/or diameter of current dual band antenna structures are sufficiently large that users, especially those who were used to relatively small single-band antenna structures, find the communication device so unwieldy (the length and thickness as well as inflexibility) that the antenna structure is often one significant sources of customer complaints. For example, when radios having current multi-band antennas are attached to the shoulder of public safety personnel (allowing the personnel e.g. to hear audio adequately in high-noise environments, e.g., a fire scene), the length of the multi-band antennas is substantial enough to interfere with movement in the direction of antenna placement, especially when equipment such as smoke masks are being used.
Accordingly, it is desirable to provide a combined antenna structure that has sufficient performance while retaining a relatively small form factor.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the embodiments of shown.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments shown so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Other elements, such as those known to one of skill in the art, may thus be present.